1. Field of the Invention
The present invention generally relates to portable communication devices, and more particularly, to providing an alert on the portable communication device entering an alerting area.
2. Description of the Related Art
Cellular networks can be used to detect the geographic location of a device. The geographic location can be estimated by different modes such as a handset based mode, network based mode, hybrid positioning mode, etc.
Network based geographic positioning systems use cellular base stations to estimate the location of the device, whereas in network assisted systems, the device estimates the location coordinates with the help of incorporated software and/or hardware applications. Further, in hybrid positioning systems, the network and the handset work together to first measure and then calculate the device's position where the device measures the data needed for location calculation and then the network calculates the geographic location. Several communication devices offer geographical positioning functionality using Global Positioning System (GPS), Assisted Global Positioning System (AGPS), Time Difference Of Arrival (TDOA), or the like.
The most basic positioning technology available for cellular systems is called cell-ID (cell identification). The communication device is associated with an individual base transceiver in a cell where every cell has a unique ID. The base transceiver recognizes the cell identity and geographic location. Further, the cell identity is also known to the communicating device, which can obtain the cell's position from the network. The accuracy of cell-ID depends solely on the dimensions and density of the cell.
GPS consists of multiple satellites which send signals containing the time stamp of sending, the orbital information and the almanac (positions of all satellites). GPS provides location and time information to the communication device, where there is an unobstructed line of sight to four or more GPS satellites. The GPS service provided to the communication device is independent of the network provider(s). The signals transmitted by GPS satellites are received by a GPS receiver in the communication device which utilizes this information to determine exact location coordinates of the device or user. A disadvantage of GPS is that it is inefficient to determine indoor positioning and further, in urban areas, the Time To First Fix (TTFF) sometimes takes a very long time because buildings hinder GPS signals from being received.
Applications on the devices can be used to create alerts which are generated when the user approaches or reaches a specific point of interest. The user initiates geographic positioning functionality by setting predefined conditions and a radius bounding the target location for presenting information on the user's communication device when the user approaches the target location. Once activated, the system continuously monitors the current location of the user's communication device through GPS, AGPS, or the like. Further, when the user reaches the proximity of the alerting area, the user is alerted using a suitable means. The user can be alerted by any means such as message, alarm, vibration, or the like.
Present day systems perform a location check of the communication device at regular intervals when the communication device is moving. The positioning is conducted relatively often, usually multiple times a minute in order to get an accurate location. Typically, position of the communication device is determined by its location calculated by the signals transmitted by satellites of the positioning system such as GPS or the like. Further, some technologies conduct positioning by means of a base station of a mobile communication network or wireless local area network (WLAN). The mobile communication network performs the positioning of the communication device and transmits information thereon to the device.
Portable communication devices typically have a limited source of power. Continuous positioning computation consumes a huge amount of power and causes increased current drain from the device battery. Increase in the power consumption of the device can restrict operating time and availability of positioning of the device. Further, portable communication devices may not have access to all satellites that are available at the mobile device location because of blocking by surrounding structures, particularly in urban and indoor environments. Since the GPS function will not be operating all of the time in order to maintain handset battery charge time, time to first fix on actuating the location function can be inordinately long for many Location Based Services (LBS) applications.